The Study On Salt Tolerance Of Three Landscape Plant Species

Height increment,leaf area increment,cell membrane permeability,chlorophyⅡcontent,MDA content,free proline content,soluble sugar content,ChlorophyⅡfluorescenc and the content of Na~+, K~+ in three tree species were searched with five different salinity(NaCl)treatments(0,0.15%,0.30%, 0.45%and 0.60%).They were Hovenia dulcis Thunb,Pistacia chinensis Bunge and Gleditsia sinensis Lam.The salt-endurance mechanism and salt tolerance ability were studied primarily.This study takes theories to biology improvement of saline land.The results obtained by the experiment were as follows:(1)With increasing NaCl,the leaf area increment and the height increment decreased.,and leaf injury was even observed.The growth of Hovenia dulcis Thunb.was inhibited over 0.15%NaCl stress, the degree of the injury is higher than Hovenia dulcis Thunb.,and the degree of the injury is the lowest in Gleditsia sinensis Lam.(2)With increasing NaCl,the chlorophyⅡfluorescence parameters such as Fv/Fm,qP andφPSⅡdecreased,but the membrane permeability,the MDA content and NPQ increased.NaCl stress leaded to the decline of chlorophyⅡand carotene contents in the leaves of Hovenia dulcis Thunb.and Pistacia chinensis Bunge,while the contents of chlorophyⅡand carotenoid increased at first and then decreased in Gleditsia sinensis Lam.with the increase of NaCl content.(3)The free proline contents of leaves of three tree species increased with the increasing of the salinity.The increasing amplitude in salt-high-tolerant species was higher than in salt-low-tolerant species(4)The soluble sugar content and protein content decreased with salinity in Hovenia dulcis,while they increased in Pistacia chinensis Bunge and Gleditsia sinensis Lam..(5)The SOD activities of Pistacia chinensis Bunge and Gleditsia sinensis Lam.increased during the process of NaCl stress.The SOD activities increased at first and then decreased in Hovenia dulcis Thunb.with the increase of NaCl content,and it reached a maximum when salt concentration is 0.15%.(6)The Na~+ contents and the ratios of Na~+ to K~+ of root,shoot and leaf of three tree species increased while the K~+ contents decreased with the increasing of salinity.The Na~+ contents and the ratios of Na~+ to K~+ of different tissue was different,root＞shoot＞leaf.Pistacia chinensis Bunge and Gleditsia sinensis Lam.accumulated less Na~+ in the leaf than in the stem and root so that the injury to the leaf can be avoided or relieved.The increasing content of Na~+ in leaves of Hovenia dulcis Thunb. was higher than Pistacia chinensis and Gleditsia sinensis,so it was damaged more seriously. (7)All the analysis shows that the sequence of the salt resistence is Gleditsia sinensis Lam.＞Pistacia chinensis Bunge＞Hovenia dulcis Thunb.